Interior rearview mirror assemblies which include a directional or compass display are known, such as the types disclosed in U.S. Pat. No. 5,802,727, which is hereby incorporated herein by reference. Typically, such mirror assemblies include a compass sensor, such as a magnetoresistive sensor, a magnetocapacitive sensor, a magnetoinductive sensor, a Hall effect sensor, or a flux gate sensor or the like, which is fixedly attached to the mirror mount that attaches the mirror assembly to a mirror assembly mounting element, such as a conventional mounting button mounted on an interior surface of the windshield of the vehicle. The mirror assemblies also include processing circuitry and a compass information display, typically included in the interior mirror casing (that includes the mirror reflector) which is pivotally adjustable by the driver to suit his or her rearward field of view.
Predominantly, compass mirror assemblies in the market today involve the fixed placement of the compass sensor (and any locally associated sensor circuitry), such as at the mirror mount where the mirror attaches to the windshield or headliner of the vehicle. The compass system typically involves a cable/harness connection to the processing circuitry (which is typically in the pivotable housing of the mirror assembly), which may include the compass compensation circuitry and the like, which feeds or connects to a display (such as a vacuum fluorescent (VF) display or the like) that is typically included in the adjustable mirror casing (such as behind the reflective element so as to display from behind and through the reflective element, or at an eyebrow or chin region of the bezel area of the mirror casing). The display then typically displays an output of the directional heading of the vehicle to the driver or passenger of the vehicle, such as an eight point display, such as N, S, E, W, NE, NW, SE, SW, or the like.
It has been proposed in the art to mount the compass sensor within the movable housing of the rearview mirror assembly. Processes have also been proposed to compensate for movement of the sensor during normal use of the mirror, such as when the mirror head or casing is adjusted by the driver. Such proposed systems, such as described in U.S. Pat. Nos. 6,140,933 and 6,023,229, which are hereby incorporated herein by reference, are often implemented with a specially adapted single ball mount or single pivot mirror assembly. Such compass mirror assemblies can be costly and often involve special tooling and complicated adaptation of the mirror assembly itself and the casing of the mirror assembly. Also, such compass systems as described in the patents referenced above are not readily adapted for use with double ball or double pivot mirror assemblies. Other compass systems and compass compensation systems, such as the types described in U.S. Pat. Nos. 4,581,827; 5,339,529; 5,455,716; 5,699,044; 5,737,226; and 5,808,197, and/or in PCT Publication No. WO 2004/076971 A2, published Sep. 10, 2004; and/or in PCT Publication No. WO 2003/044540, published May 30, 2003; and/or in PCT Publication No. WO 2003/074969, published Sep. 12, 2003 (which are all hereby incorporated herein by reference), may be implemented in interior rearview mirror assemblies, but may be costly and difficult to implement within the movable mirror head of an interior rearview mirror assembly with a single or double ball mounting arrangement.
Therefore, there is a need in the art for an interior rearview mirror assembly having a compass system associated therewith that overcomes the shortcomings of the prior art.